Rooney has a mixed record with penalties and became the fourth United player to miss one this season when he struck wide in United's 2-1 Premier League victory over Arsenal at Old Trafford on Saturday.

However, he stepped forward again when United were awarded a penalty with five minutes remaining at the Estádio Axa, and appeared to skid on the wet surface as he fired the ball in. He conceded afterwards that he had been "a bit fortunate".

Asked if he had had any doubts about taking the penalty, Rooney said: "No, not at all. Obviously I was disappointed at the weekend, not only to miss but to miss the target.

"I said after the game it wasn't good enough and [against Braga] I was a bit fortunate. I slipped but thankfully it's gone in so I'm happy with that. At the time it happened so quick, but obviously I've seen it going towards the goal and the keeper going the other way.

"I was happy with it going in but obviously I've been quite lucky with that."

With Javier Hernández adding a close-range finish in stoppage-time, United went on to complete a 3-1 victory, their fourth win in four Group H fixtures, which guarantees them top spot and a place in the last 16.

"I think we can play better football," Rooney said. "At times it was too slow but the result is the most important thing.

"I think we had quite a bit of possession, we just needed a bit more movement and speed to our play, and thankfully in the last 10 or 15 minutes, when it mattered, we got them."

Ryan Giggs, who came into the starting lineup as one of six changes from the Arsenal game, felt the introduction of Robin van Persie shortly after the resumption of play following the power cut was crucial.

"It wasn't until after we went 1-0 down – probably when Robin came on – that we started to play a little bit better," Giggs, 38, said. "His confidence is just sky high at the moment.

"I read last week that a lot of the players think he's similar to Ruud [van Nistelrooy] in the respect that Ruud used to get a chance and more often than not he'd put them away.

"That's the case with Robin at the minute; his confidence is high, we're creating chances for him and he's putting them away."

With a maximum 12 points, United are eight points clear of Galatasaray and CFR Cluj in Group H, and nine in front of Braga, with two rounds of group games to go.